Regioselective Photoallylation of Furyl and Thienyl Dicyanoethenes by Allylic Stannanes via Photoinduced Electron Transfer

Abstract

Irradiation of 1,1-dicyano-2-(2-furyl)ethene and allyltributylstannane in the presence of phenanthrene in aqueous acetonitrile afforded regioselectively 5,5-dicyano-4-(2-furyl)-1-pentane. Photoreactions of the other furyl and thienyl dicyanoethene derivatives with allylic stannanes gave the corresponding allylic products in good yields.

Diastereoselective protonation on a radical anion in the photoallylation and photoreduction of 1,1-dicyano-2-methyl-3-phenyl-1-butene by allyltrimethylsilane

“…Photoinduced electron transfer (PET) reaction between organosilicon compounds and electron-deficient molecules is a powerful tool for organic synthesis [1][2][3][4][5][6][7][8][9][10][11]. In these photoreactions, radical anions generated from the electron-deficient molecules and carbon radicals generated from radical cations of the organosilicon compounds are postulated as reactive intermediates.…”

Electron-Transfer-Photosensitized Conjugate Alkylation

“…The thus-formed alkylated derivatives were isolated by bulb-to-bulb distillation or by column chromatography. Extending the previously reported initial attempt,3a the reaction was tested with various alkenes, such as methyl acrylate ( 1a ), methyl crotonate ( 1b ), acrylonitrile ( 1c ), and dimethyl maleate ( 1d ). Under these conditions irradiation with tetrabutylstannane ( 2 ) gave the corresponding alkylated derivatives 3a − d in medium to good yield (Scheme ).…”

“…Although back-electron transfer cuts down the lifetime of the thus-formed radical ion pair, fragmentation of the radical cation is sufficiently fast in a number of cases to give neutral alkyl radicals with a reasonable (0.1 or higher) quantum yield. , In turn, the radical is trapped by the long-lived nitrile radical anion, and aromatic substitution is the final result (Scheme , path a). However, the radical can also add to a neutral trap, and indeed, we recently showed that radicalic alkylation of electron-withdrawing substituted alkenes can be obtained under this condition, with the aromatic nitrile (or alternatively an aromatic ester, in this case via the triplet state) functioning as a nonconsumed sensitizer , path b, represents a novel redox sequence for radicalic alkene alkylation in which the educt radical is generated through an oxidative step and the final product arises from the adduct radical via a reductive step 3a.…”

“…However, the radical can also add to a neutral trap, and indeed, we recently showed that radicalic alkylation of electron-withdrawing substituted alkenes can be obtained under this condition, with the aromatic nitrile (or alternatively an aromatic ester, in this case via the triplet state) functioning as a nonconsumed sensitizer , path b, represents a novel redox sequence for radicalic alkene alkylation in which the educt radical is generated through an oxidative step and the final product arises from the adduct radical via a reductive step 3a. Therefore, the method may have preparative value.…”

Electron‐transfer Organic and Bioorganic Photochemistry

“…,1985h, , 1988a. Similarly, lI1-dicyano-2-(2-thienyl or 2-fury1)ethylenes are photoallylated with allyltrimethylstannane to give 2allylated products in good yields (Mizuno et al, 1987a(Mizuno et al, , 1987b. Irradiation of ArCH,M(CH& (Ar = phenyl, naphthyl and 9-phenanthryl; M = Si, Sn, and Ge) in the presence of Cu(I1) salt in methanol gives the corresponding arylmethyl methyl ethers, products arising from leoxidation of arylmethyl radicals by Cu(I1) ion (Mizuno et al, 1988b).…”